How did sexual reproduction evolve?

How did sexual reproduction get started? This is a huge problem for evolution because for some things we can say they had millions of years but when it comes to organisms sexually reproducing, you don’t have millions of years. You have the lifetime of that creature, for that creature to develop a fully functioning reproductive system and find a mate that has a complementary fully formed reproductive system. And the reproductive systems that we observe in organisms are incredibly complex. These aren’t the kind of things that just spontaneously form. We don’t observe reproductive systems spontaneously forming so how does evolution explain this? Well, it doesn’t at all. And if you do a search right now and you start looking for research done on this, you’re going to find articles about possibilities, speculative stories and you’re going to find ideas about why reproduction what sexual reproduction was beneficial but how it happened, nobody has a clue.